as any if you want to study the history of our planet, you know, basically when you look at the wall of the grand canyon which goes down a mile you are reading a his three book, you just need to know how to read the boxes-- rocks. and the deeper you go the further back there time go. $2 billion years that is about half the planet right there. so geologist love the story that they cun fold there, it tells them a lot about erosion, it tells them about tetonic, volcanoism, and it gives them a glisless-- glimpse into the early days of our planet without having to drill a deep ohl. and then there are the 5 million of us that just like to go and go wow. >> warner: i guess the question is are they going to have to change the lecture what do they call, the trail of time or something that they have. >> the trail of time just got much longer, carl says no, he's going to make sure that they don't do that. so there will be further, i guess we can say stay tuned on this one. >> warner: we'll stay tuned, maybe not for 6 million years, miles o'brien, thank you. >> pleasure, margaret.